Apparatus and method for allocating resources for switching between macro cell and small cell in wireless communication system

ABSTRACT

The objective of the present invention is to provide services by effectively switching, by a terminal, a macro cell and a small cell on the basis of time in a communication system in which the macro cell and the small cell coexist. A method for operating a terminal in a wireless communication system comprises the steps of: transmitting, to a first base station and/or a second base station, information on a switching delay time required for the terminal to perform cell switching; and communicating through a resource of the first base station and a resource of the second base station which are allocated by considering the switching delay time.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 14/914,973, filed on Feb. 26, 2016, which is a U.S. National Stageapplication under 35 U.S.C. § 371 of an International application filedon Aug. 26, 2014 and assigned application number PCT/KR2014/007947,which claimed the benefit of a Korean patent application filed on Aug.26, 2013 in the Korean Intellectual Property Office and assigned Serialnumber 10-2013-0101206, the entire disclosure of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to resource allocation in a wirelesscommunication system in which a macro cell and a small cell coexist.

BACKGROUND

Wireless communication systems are in rapid development and,particularly, in recent years, are being developed in a form ofsupporting a high-speed large-capacity data service in order to satisfyusers' various desires. As one way for the high-speed large-capacitydata service, installing a small cell as well as an existing macro cellis being taken into consideration.

Commonly, the small cell is installed at a higher frequency band thanthe macro cell and thus can support a higher data rate than the macrocell. Particularly, in case that the existing macro cell is difficult tosupport a new service, the small cell supporting the higher data rate isused to support the new service, whereby effective network operation ispossible.

In case that the macro cell and the small cell are installed together,it is common that a terminal is serviced only in one cell among themacro cell or the small cell. Hence, further, being serviced from thetwo cells after forming a connectivity, i.e., a dual connectivity in allof the macro cell and the small cell is being taken into consideration.

SUMMARY

Accordingly, one exemplary embodiment of the present invention providesan apparatus and method for supporting a dual connectivity for aplurality of base stations in a wireless communication system.

Another exemplary embodiment of the present invention provides anapparatus and method for effectively using a resource at dualconnectivity in a wireless communication system.

A further exemplary embodiment of the present invention provides anapparatus and method for preventing a conflict between resources at dualconnectivity in a wireless communication system.

A yet another exemplary embodiment of the present invention provides anapparatus and method for providing information necessary for resourcecoordination for resource conflict prevention in a wirelesscommunication system.

A still another exemplary embodiment of the present invention providesan apparatus and method for indicating a scheduling type in a dualconnectivity in a wireless communication system.

A still another exemplary embodiment of the present invention providesan apparatus and method for recognizing a resource conflict in awireless communication system.

A still another exemplary embodiment of the present invention providesan apparatus and method for preventing unnecessary cell switching atdual connectivity in a wireless communication system.

A method for operating a terminal in a wireless communication systemaccording to an exemplary embodiment of the present invention,characterized in that the method includes the steps of transmittinginformation on a switching delay time required for the terminal toperform cell switching to at least one of a first base station and asecond base station, and performing communication through a resource ofthe first base station and a resource of the second base station whichare allocated by considering the switching delay time.

A method for operating a first base station in a wireless communicationsystem according to another exemplary embodiment of the presentinvention, characterized in that the method includes the steps ofreceiving information on a switching delay time required for a terminalto perform cell switching between the first base station and a secondbase station from the terminal, and performing communication with theterminal through a resource which is allocated by considering theswitching delay time.

A terminal apparatus in a wireless communication system according to afurther exemplary embodiment of the present invention, characterized inthat the apparatus includes a transmitter transmitting information on aswitching delay time required for the terminal to perform cell switchingto at least one of a first base station and a second base station, and acontroller controlling to perform communication through a resource ofthe first base station and a resource of the second base station whichare allocated by considering the switching delay time.

A first base station apparatus in a wireless communication systemaccording to a yet another exemplary embodiment of the presentinvention, characterized in that the apparatus includes a receiverreceiving information on a switching delay time required for a terminalto perform cell switching between the first base station and a secondbase station from the terminal, and a controller controlling to performcommunication with the terminal through a resource which is allocated byconsidering the switching delay time.

Various exemplary embodiments of the present invention make it possiblefor a terminal to perform a procedure of efficiently switching on thebasis of time between a macro cell and a small cell and being servicedin a communication system in which the macro cell and the small cellcoexist, thereby dispersing a load of the macro cell to the small cell.

Also, various exemplary embodiments of the present invention maydifferentiate, according to a switching capability of a terminal, aresource required for the terminal to switch on the basis of timebetween a macro cell and a small cell and be serviced in a communicationsystem in which the macro cell and the small cell coexist.

Also, various exemplary embodiments of the present invention efficientlycontrol a time-based switching time point between a macro cell and asmall cell in a communication system in which the macro cell and thesmall cell coexist, thereby decreasing power consumption of a terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a diagram schematically illustrating a wireless communicationsystem in which a macro cell and a small cell coexist according to anexemplary embodiment of the present invention;

FIGS. 2A, 2B, and 2C are diagrams illustrating time based switchingbetween a macro cell and a small cell in a wireless communication systemaccording to an exemplary embodiment of the present invention;

FIG. 3 is a diagram illustrating resource use for cell switching in acommunication system according to a first exemplary embodiment of thepresent invention;

FIG. 4 is a diagram illustrating resource use for cell switching in acommunication system according to a second exemplary embodiment of thepresent invention;

FIG. 5 is a diagram illustrating resource use for cell switching in acommunication system according to a third exemplary embodiment of thepresent invention;

FIG. 6 is a diagram illustrating resource use for cell switching in acommunication system according to a fourth exemplary embodiment of thepresent invention;

FIG. 7 is a diagram illustrating resource use for cell switching in acommunication system according to a fifth exemplary embodiment of thepresent invention;

FIG. 8 is a diagram illustrating a signal exchange for resource use in awireless communication system according to an exemplary embodiment ofthe present invention;

FIG. 9 is a diagram illustrating a signal exchange for resource use in awireless communication system according to another exemplary embodimentof the present invention;

FIG. 10 is a diagram illustrating a signal exchange for processing aconflict of resource allocation in a wireless communication systemaccording to an exemplary embodiment of the present invention;

FIG. 11 is a diagram illustrating a signal exchange for resource use ina wireless communication system according to a further exemplaryembodiment of the present invention;

FIG. 12 is a diagram illustrating a signal exchange for resource use ina wireless communication system according to a yet another exemplaryembodiment of the present invention;

FIG. 13 is a diagram illustrating a signal exchange for resourceallocation monitoring in a wireless communication system according to anexemplary embodiment of the present invention;

FIG. 14 is a diagram illustrating a signal exchange for scheduling typedetermination in a wireless communication system according to anexemplary embodiment of the present invention;

FIG. 15 is a diagram illustrating a signal exchange for scheduling typedetermination in a wireless communication system according to anotherexemplary embodiment of the present invention;

FIG. 16 is a diagram illustrating an operation procedure of a terminalin a wireless communication system according to an exemplary embodimentof the present invention;

FIG. 17 is a diagram illustrating an operation procedure of a terminalin a wireless communication system according to another exemplaryembodiment of the present invention;

FIG. 18 is a diagram illustrating an operation procedure of a terminalin a wireless communication system according to a further exemplaryembodiment of the present invention;

FIG. 19 is a diagram illustrating an operation procedure of a terminalin a wireless communication system according to a yet another exemplaryembodiment of the present invention;

FIG. 20 is a diagram illustrating an operation procedure of a macro basestation in a wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 21 is a diagram illustrating an operation procedure of a macro basestation in a wireless communication system according to anotherexemplary embodiment of the present invention;

FIG. 22 is a diagram illustrating an operation procedure of a macro basestation in a wireless communication system according to a furtherexemplary embodiment of the present invention;

FIG. 23 is a diagram illustrating an operation procedure of a small cellbase station in a wireless communication system according to anexemplary embodiment of the present invention;

FIG. 24 is a diagram illustrating a block construction of a terminal ina wireless communication system according to an exemplary embodiment ofthe present invention; and

FIG. 25 is a diagram illustrating a block construction of a base stationin a wireless communication system according to an exemplary embodimentof the present invention.

DETAILED DESCRIPTION

Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In describing thepresent invention, well-known functions or constructions are notdescribed in detail since they would obscure the invention inunnecessary detail. And, terms described below, which are definedconsidering functions in the present invention, can be modified inaccordance to user and operator's intention or practice. Therefore, thedefinition should be given on the basis of the content throughout thepresent specification.

The present invention describes a technology for effectively performing,by a terminal, switching between a macro cell and a small cell in acommunication system in which the macro cell and the small cell coexist.

For description's convenience below, the present invention uses some ofthe terms and names defined in the 3GPP LTE (3rd Generation PartnershipProject Long Term Evolution) standard. However, the present invention isnot limited to the terms and names, and may be identically applied evento systems following other standards.

FIG. 1 schematically illustrates a wireless communication system inwhich a macro cell and a small cell coexist according to an exemplaryembodiment of the present invention.

Referring to the FIG. 1, the wireless communication system includes aterminal 110, a macro base station 120, a small cell base station 130,an access control router 140, a serving gateway (S-GW) 150, and a packetgateway (P-GW) 160.

The terminal 110 is a user device. The terminal 110 may be a smartphone,or a device designed for data communication only. The terminal 110 mayconnect to the macro base station 120, the small cell base station 130.

The macro base station 120 and the small cell base station 130 provide awireless connection to the terminal 110, thereby supporting aconnectivity between the terminal 110 and a network. Cells of the macrobase station 120 and the small cell base station 130 may be overlappedwith each other. The macro base station 120 and the small cell basestation 130 are divided according to relative sizes and hierarchicalrelations of cells. Accordingly, the small cell base station 130 may beinstalled for various purposes such as sharing, supplementing of a roleof the macro base station 120, a separate service, etc. In detail, themacro base station 120 and the small cell base station 130 may benetwork entities belonging to the same system. For another example, themacro base station 120 and the small cell base station 130 may benetwork entities belonging to different systems (e.g., cellular,wireless LAN). That is, the macro base station 120 may be a cellularbase station, and the small cell base station 130 may be an AP (AccessPoint).

The access control router 140 manages the mobility of the terminal 110.Also, the access control router 140 may further perform authenticationon the terminal 110, bearer management, etc. The access control router140 may be called an ‘MME (Mobility Management Entity)’.

The serving gateway 150 processes packets arrived from the macro basestation 120 and the small cell base station 130 or packets to beforwarded to the macro base station 120 and the small cell base station130. Also, the serving gateway 150 may perform an anchoring role athandover of the terminal 110. The packet gateway 160 may function as aconnectivity point with an external network (e.g., the Internetnetwork). Also, the packet gateway 160 allocates an IP (InternetProtocol) address to the terminal 110.

The macro base station 120 is connected with the access control router140, the serving gateway 150. The small cell base station 130 isconnected with the serving gateway 150. In accordance with anotherexemplary embodiment of the present invention, the small cell basestation 130 may not have a connectivity with the serving gateway 150.The small cell base station 130 is connected with the macro base station120. Also, a plurality of small cell base stations 130 construct a smallcell cluster. The terminal 110 may be connected to the macro basestation 120, or be connected to the small cell base station 130, or forma dual connectivity to the macro base station 120 and the small cellbase station 130.

As described above, a terminal may form a dual connectivity with a macrobase station and a small cell base station. Accordingly to this, theterminal may concurrently transmit/receive data with all of a macro celland a small cell. But, in case that the terminal is a hardware devicedifficult to set a simultaneous connectivity to the macro cell and thesmall cell, particularly, in case of uplink, there may be a limit inperforming service through the simultaneous connectivity due to adifference of a transmission power in the macro cell and the small cell.

The macro cell may provide service at a low frequency band, and thesmall cell may provide service at a high frequency band not adjacentwith the macro cell. In this case, setting to receive a support of ahigh data rate only from the small cell may be more advantageous thanimplementing a complex hardware in a terminal in order to set asimultaneous connectivity to the macro cell and the small cell andtransmit/receive data.

Therefore, in accordance with an exemplary embodiment of the presentinvention, time durations connected to the macro cell and the small cellare separated, whereby a terminal may be serviced from all of the macrocell and the small cell. At this time, a resource allocated in order forthe terminal to transmit/receive data in the macro cell and the smallcell should be allocated in consideration of a time required for theterminal to switch a cell. However, if a resource is allocated withoutconsidering the time required to switch, some resources may be discardedwithout being used. For example, if an uplink resource is allocatedwithout considering the time required to switch, an uplink resourceallocated while the terminal switches from the macro cell to the smallcell or in a duration in which it switches from the small cell to themacro cell cannot be used by the terminal.

Accordingly, various exemplary embodiments of the present inventionpropose a way of resource use of the macro cell and the small cell.

FIG. 2A to FIG. 2C illustrate time based switching between a macro celland a small cell in a wireless communication system according to anexemplary embodiment of the present invention.

Referring to the FIG. 2A, a terminal1 211 is located within serviceareas of a macro base station 220 and a small cell base station 230, anda terminal2 212 is located within a service area of the macro basestation 220. The terminal1 211 is serviced during a time duration (t)through the macro base station 220. If the time duration (t) is ended,the terminal1 211 switches to the small cell base station 230 and then,is serviced during a time duration (t+1) through the small cell basestation 230. If the time duration (t+1) is ended, the terminal1 211switches to the macro base station 220, and is serviced through themacro base station 220 during a time duration (t+2).

FIG. 2B illustrates one example of time arrangement in which theterminal1 211 performs time based switching between the macro basestation 220 and the small cell base station 230. The macro base station220 services a control signal of the terminal1 211, and the small cellbase station 230 services user data of the terminal1 211. A controlsignal frame and user data frame for the terminal1 211 may be defined ata time point at which the terminal1 211 initiates a dual connectivity tothe macro base station 220 and the small cell base station 230. Forexample, the control signal frame may be used in order for the terminal1211 to exchange, with the macro base station 220, a signal forperforming a channel measurement report or an operation of an RRC (RadioResource Control) layer. The user data frame is used in order for theterminal1 211 to exchange, with the small cell base station 230, packetsof service (data or voice) to be received. At this time, the macro basestation 220 does not need to maintain a resource (e.g., bearerconnectivity information) for processing the user data.

The FIG. 2C illustrates another example of time arrangement in which theterminal1 211 performs time based switching between the macro basestation 220 and the small cell base station 230. Referring to the FIG.2C, the macro base station 220 services a control signal and userdownlink data of the terminal1 211, and the small cell base station 230services user downlink data and uplink data of the terminal 211. In caseof the user downlink data, the terminal1 211 may be concurrentlyserviced from the macro base station 220 and the small cell base station230, or may be serviced from one of the macro base station 220 and thesmall cell base station 230. The user uplink data is serviced only bythe small cell base station 230. Therefore, in accordance with a servicetime point of the user uplink data, the terminal1 211 performs timebased switching to the small cell base station 230. Accordingly to this,the macro base station 220 does not need to maintain a resource (e.g.,bearer connectivity information) for the user uplink data.

In another example of the time based switching between the macro basestation and the small cell base station, the macro cell and small cellmay provide services of different types. In this case, a terminal mayperform time based switching between the macro base station and thesmall cell base station in accordance with a service time point of themacro cell and a service time point of the small cell.

FIG. 3 illustrates resource use for cell switching in a communicationsystem according to a first exemplary embodiment of the presentinvention.

Referring to the FIG. 3, a macro base station and a small cell basestation each transmit scheduling information, i.e., resource allocationinformation for a terminal. In detail, the macro base station indicatesa resource 304 allocated in its own downlink frame through downlinkscheduling information 302, a resource 314 allocated in its own uplinkframe through uplink scheduling information 312. And, the small cellbase station indicates a resource 324 allocated in its own downlinkframe through downlink scheduling information 322, a resource 334allocated in its own uplink frame through uplink scheduling information332. Accordingly to this, the terminal receives downlink data andtransmits uplink data with each base station through the resourcechecked by the resource allocation information from each of the macrobase station and the small cell base station.

The terminal may receive downlink data from each of base stationswithout switching between the macro cell and the small cell. However, incase of transmitting uplink data, the terminal needs switching betweenthe macro cell and the small cell. At this time, a certain time delayoccurs for the switching. Therefore, when the macro base station and thesmall cell base station allocate an uplink resource for the terminal, atime required for the switching of the terminal should be taken intoconsideration. The time required for the switching is related to ahardware capability of the terminal and therefore, may be provided to abase station during a capability negotiation procedure of an initialconnection procedure of the terminal or a procedure proportional tothis. For description's convenience below, the present invention callsthe ‘certain time required for the cell switching related to thehardware capability of the terminal’, a ‘switching delay time’.Switching delay time information of the terminal may be provided to themacro base station by the terminal, and may be forwarded to the smallcell base station by the macro base station. Or, the terminal mayprovide to the macro base station and the small cell base station.

The FIG. 3 illustrates an exemplary embodiment of a TDD scheme in whicha downlink frame and an uplink frame are divided by time. However, inaccordance with another exemplary embodiment of the present invention,the resource use illustrated in the FIG. 3 may be applied identicallyeven in case of an FDD (Frequency Division Multiplexing) scheme in whichuplink and downlink are divided by a frequency.

FIG. 4 illustrates resource use for cell switching in a communicationsystem according to a second exemplary embodiment of the presentinvention.

Referring to the FIG. 4, a macro base station and a small cell basestation each transmit scheduling information, i.e., resource allocationinformation for a terminal. In detail, the macro base station indicatesa resource 404 allocated in its own downlink frame through downlinkscheduling information 402, a resource 414 allocated in its own uplinkframe through uplink scheduling information 412. And, the small cellbase station indicates a resource 424 allocated in its own downlinkframe through downlink scheduling information 422, a resource 434allocated in its own uplink frame through uplink scheduling information432. Accordingly to this, the terminal receives downlink data andtransmits uplink data with each base station through the resourcechecked by the resource allocation information from each of the macrobase station and the small cell base station.

The terminal may receive downlink data from each of base stationswithout switching between the macro cell and the small cell. However, incase of transmitting uplink data, the terminal needs switching betweenthe macro cell and the small cell. At this time, a certain time delayoccurs for the switching. Therefore, when the macro base station and thesmall cell base station allocate an uplink resource of the terminal, aswitching delay time of the terminal should be taken into consideration.Further, unlike the exemplary embodiment illustrated in the FIG. 3, evena TA (Timing Advance) caused by a propagation delay between the terminaland the base station should be considered. The TA means how earlier asignal should be transmitted than desired timing in order for the signalto reach a receive end at the timing. The TA increases as a distancebetween the terminal and the base station increases. The TA informationmay be acquired through an RACH (Random Access Channel) procedure or anRA (Random Access) procedure the terminal performs with each basestation. The terminal may provide TA information on the small cell basestation to the macro base station, and provide TA information on themacro base station to the small cell base station. Or, the macro basestation and the small cell base station may directly exchange TAinformation of the terminal. The macro base station and the small cellbase station determine a cell switching time of the terminal on thebasis of the switching delay time of the terminal, TAs. And, the macrobase station and the small cell base station allocate an uplink resourcefor the terminal in consideration of the cell switching time of theterminal.

The FIG. 4 illustrates an exemplary embodiment of a TDD scheme in whicha downlink frame and an uplink frame are divided by time. However, inaccordance with another exemplary embodiment of the present invention,the resource use illustrated in the FIG. 4 may be applied identicallyeven in case of an FDD scheme in which uplink and downlink are dividedby a frequency.

FIG. 5 illustrates resource use for cell switching in a communicationsystem according to a third exemplary embodiment of the presentinvention.

Referring to the FIG. 5, a macro base station transmits schedulinginformation, i.e., resource allocation information for a terminal. Indetail, the macro base station indicates a resource 504 allocated in itsown downlink frame through downlink scheduling information 502 and aresource 506 allocated in a downlink frame of a small cell base station,a resource 514 allocated in its own uplink frame through uplinkscheduling information 512 and a resource 516 allocated in an uplinkframe of the small cell base station. Accordingly to this, the terminalreceives downlink data and transmits uplink data with each base stationthrough the resource checked by the resource allocation information fromthe macro base station.

Similarly to the exemplary embodiment illustrated in the FIG. 4, whenthe macro base station allocates an uplink resource of the terminal, aswitching delay time of the terminal and TAs are considered. That is,the macro base station determines a cell switching time of the terminalon the basis of the switching delay time of the terminal, the TAs, andallocates the uplink resource for the terminal in consideration of thecell switching time of the terminal.

The FIG. 5 illustrates an exemplary embodiment of a TDD scheme in whicha downlink frame and an uplink frame are divided by time. However, inaccordance with another exemplary embodiment of the present invention,the resource use illustrated in the FIG. 5 may be applied identicallyeven in case of an FDD scheme in which uplink and downlink are dividedby a frequency.

FIG. 6 illustrates resource use for cell switching in a communicationsystem according to a fourth exemplary embodiment of the presentinvention.

Referring to the FIG. 6, a macro base station transmits schedulinginformation, i.e., resource allocation information for a terminal. Indetail, the macro base station indicates a resource 604 allocated in itsown downlink frame through downlink scheduling information 602 and aresource 606 allocated in a downlink frame of a small cell base station,a resource 614 allocated in its own uplink frame through uplinkscheduling information 612 and a resource 616 allocated in an uplinkframe of the small cell base station. Accordingly to this, the terminalreceives downlink data and transmits uplink data with each base stationthrough the resource checked by the resource allocation information fromthe macro base station.

Unlike the exemplary embodiments illustrated in the FIG. 3 to the FIG.5, in case of the exemplary embodiment illustrated in the FIG. 6, evendownlink data reception is accompanied by switching. Accordingly tothis, when a downlink resource and an uplink resource are allocated forthe terminal, a switching delay time of the terminal and TAs areconsidered. That is, the macro base station determines a cell switchingtime of the terminal on the basis of the switching delay time of theterminal, the TAs, and allocates the downlink resource and the uplinkresource for the terminal in consideration of the cell switching time ofthe terminal.

The FIG. 6 illustrates an exemplary embodiment of a TDD scheme in whicha downlink frame and an uplink frame are divided by time. However, inaccordance with another exemplary embodiment of the present invention,the resource use illustrated in the FIG. 6 may be applied identicallyeven in case of an FDD scheme in which uplink and downlink are dividedby a frequency.

FIG. 7 illustrates resource use for cell switching in a communicationsystem according to a fifth exemplary embodiment of the presentinvention.

Referring to the FIG. 7, a macro base station and a small cell basestation each transmit scheduling information, i.e., resource allocationinformation for a terminal. In detail, the macro base station indicatesa resource 704 allocated in its own downlink frame through downlinkscheduling information 702, a resource 714 allocated in its own uplinkframe through uplink scheduling information 712. And, the small cellbase station indicates a resource 724 allocated in its own downlinkframe through downlink scheduling information 722, a resource 734allocated in its own uplink frame through uplink scheduling information732. Accordingly to this, the terminal receives downlink data andtransmits uplink data with each base station through the resourcechecked by the resource allocation information from each of the macrobase station and the small cell base station.

Unlike the exemplary embodiments of the FIG. 3 to the FIG. 6, in case ofthe FIG. 7, switching is performed by the unit of frame. That is, onespecific frame is used for communication with the macro base station orthe small cell base station, and the other specific frame is used forcommunication with the small cell base station or the macro basestation. Accordingly, a terminal receives only scheduling information onone base station in one frame. In this case, a time for cell switchingbetween an uplink resource in an uplink frame of a front end on a basisof switching and a control channel including scheduling information in adownlink frame of a rear end is provided. Generally, a position of thecontrol channel is fixed within a frame and therefore, when the uplinkresource in the uplink frame of the front end is allocated, a switchingdelay time of the terminal and TAs should be considered.

The FIG. 7 illustrates an exemplary embodiment of a TDD scheme in whicha downlink frame and an uplink frame are divided by time. However, inaccordance with another exemplary embodiment of the present invention,the resource use illustrated in the FIG. 7 may be applied identicallyeven in case of an FDD scheme in which uplink and downlink are dividedby a frequency.

As described above, it is required to guarantee a time to performswitching between a macro cell and a small cell. In other words, it isrequired that a certain interval between a resource region allocated inthe macro cell and a resource region allocated in the small cell exists.The interval between the resource regions may be provided throughvarious procedures. For example, in accordance with an exemplaryembodiment of the present invention, the time to perform the switchingmay be secured by setting not to allocate a certain resource region.

For example, in case that resources are allocated in order of a resourceof a macro cell, a resource of a small cell on time axis, a resource tobe empty may be set to the resource of the small cell for a sum or moreof the resource of the macro cell and a resource of a cell switchingtime. For description's convenience below, the present invention callsthe ‘resource to make empty’ a ‘resource empty’. The resource empty maybe defined as at least one unit among a symbol, a slot, a subframe. Theresource empty is set to at least one of the resource of the macro celland the resource of the small cell.

FIG. 8 illustrates a signal exchange for resource use in a wirelesscommunication system according to an exemplary embodiment of the presentinvention.

Referring to the FIG. 8, in step 801, a terminal 810 performs an RACHprocedure with a macro base station 820 during an initial connectionprocedure. For example, the terminal 810 selects a resource for randomaccess, and transmits a random access preamble, and then receives arandom access response from the macro base station 820. Through the RACHprocedure, the terminal 810 and the macro base station 820 may acquireTA information on the macro base station 820. For example, the macrobase station 820 estimates a transmission timing of the terminal 810using the random access preamble, and transmits a TA command related toa TA through the random access response.

In step 803, the terminal 810 transmits capability information includinga switching delay time to the macro base station 820. The capabilityinformation may include information on other hardware, softwarecapability besides the switching delay time. In accordance with anotherexemplary embodiment of the present invention, the switching delay timemay be forwarded through a separate procedure or a separate message.

In step 805, if a small cell base station 830 to service the terminal810 is determined, the terminal 810 performs an RACH procedure so as toconnect to the small cell base station 830. Through the RACH procedure,the terminal 810 may acquire TA information on the small cell basestation 830. For example, the terminal 810 selects a resource for randomaccess, and transmits a random access preamble, and then receives arandom access response from the macro base station 820. Through the RACHprocedure, the terminal 810 and the macro base station 820 may acquireTA information on the macro base station 820. For example, the macrobase station 820 estimates a transmission timing of the terminal 810using the random access preamble, and transmits a TA command related toa TA through the random access response.

In step 807, the terminal 810 reports the TA information on the smallcell base station 830 to the macro base station 820. Here, the TAinformation may directly or indirectly express, by the unit of time,resource, etc., a difference of time between a time point oftransmission in the terminal 810 and a time point of reception in thesmall cell base station 830.

In step 809, the terminal 810 reports the TA information on the macrobase station 820 to the small cell base station 830. Here, the TAinformation may directly or indirectly express, by the unit of time,resource, etc., a difference of time between a time point oftransmission in the terminal 810 and a time point of reception in themacro base station 820.

In step 811, the terminal 810 transmits capability information includingswitching delay time information of the terminal 810 to the small cellbase station 830. The capability information may include information onother hardware, software capability besides the switching delay time. Inaccordance with another exemplary embodiment of the present invention,the switching delay time may be forwarded through a separate procedureor a separate message.

In step 813, the macro base station 820 and the small cell base station830 coordinate resource allocation for the terminal 810. For this, themacro base station 820 and the small cell base station 830 may exchangeinformation of a required resource amount, an available resource amount,a position (e.g., frame, subframe, symbol/slot/sub channel position,etc.) of a resource to be actually allocated, etc. In detail, the macrobase station 820 and the small cell base station 830 determine a cellswitching time based on the switching delay time of the terminal 810 andthe TAs. At this time, the macro base station 820 and the small cellbase station 830 determine a resource empty in consideration of the cellswitching time of the terminal 810. The resource empty may be expressedby the unit of frame, subframe, slot, symbol, etc. For example, theresource empty may be used to make empty a certain duration in the lastsubframe of macro base station downlink, or in the first subframe ofmacro base station uplink, or in the last subframe of small cell basestation downlink, or in the first subframe of small cell base stationuplink. In accordance with one exemplary embodiment of the presentinvention, information on the resource empty may be forwarded even tothe terminal 810. For example, the information on the resource empty maybe provided as a part of the resource allocation information provided tothe terminal 810. If the macro base station 820 and the small cell basestation 830 are network entities belonging to different systems,information provided between the macro base station 820 and the smallcell base station 830 may be transmitted after being processed into aform interpretable at a reception side, or the reception side may have acapability capable of interpreting a format of a transmission sidesystem. Or, a third entity for processing of the information exists, andthe third entity may process and forward the information.

In step 815, the macro base station 820 allocates a resource for theterminal 810 in consideration of the cell switching time of the terminal810, a resource state, and transmits resource allocation information.

In step 817, the small cell base station 830 allocates a resource forthe terminal 810 in consideration of the cell switching time of theterminal 810, a resource state, and transmits resource allocationinformation. At this time, in case that the resource empty is set in aresource of the small cell base station 830, the small cell base station830 allocates a resource to the terminal 810 in the remnant regionexcepting the resource empty. For example, if the resource empty is twosubframes of an uplink region, the small cell base station 830 allocatesa resource to the terminal 810 in the remnant region excepting twosubframes of a front end of the uplink region.

FIG. 9 illustrates a signal exchange for resource use in a wirelesscommunication system according to another exemplary embodiment of thepresent invention.

Referring to the FIG. 9, in step 901, a terminal 910 performs an RACHprocedure with a macro base station 920 for the sake of initialconnection. For example, the terminal 910 selects a resource for randomaccess, and transmits a random access preamble, and then receives arandom access response from the macro base station 920. Through the RACHprocedure, the terminal 910 and the macro base station 920 may acquireTA information on the macro base station 920. For example, the macrobase station 920 estimates a transmission timing of the terminal 910using the random access preamble, and transmits a TA command related toa TA through the random access response.

In step 903, the terminal 910 transmits capability information includinga switching delay time to the macro base station 920. The capabilityinformation may include information on other hardware, softwarecapability besides the switching delay time. In accordance with anotherexemplary embodiment of the present invention, the switching delay timemay be forwarded through a separate procedure or a separate message.

In step 905, if a small cell base station 930 the terminal 910 is toconnect is determined, the macro base station 920 provides, to the smallcell base station 930, a switching delay time of the terminal 910 and TAinformation on the macro base station 920. Here, the TA information maydirectly or indirectly express, by the unit of time, resource, etc., adifference of time between a time point of transmission in the terminal910 and a time point of reception in the macro base station 920.

In step 907, the terminal 910 performs an RACH procedure so as toconnect to the small cell base station 930. Through the RACH procedure,the small cell base station 920 may acquire TA information on the smallcell base station 930. For example, the terminal 910 selects a resourcefor random access, and transmits a random access preamble, and thenreceives a random access response from the small cell base station 930.Through the RACH procedure, the terminal 910 and the small cell basestation 930 may acquire TA information on the small cell base station930. For example, the small cell base station 930 estimates atransmission timing of the terminal 910 using the random accesspreamble, and transmits a TA command related to a TA through the randomaccess response.

In step 909, the small cell base station 930 transmits, to the macrobase station 920, the TA information on the small cell base station 930of the terminal 910. Here, the TA information may directly or indirectlyexpress, by the unit of time, resource, etc., a difference of timebetween a time point of transmission in the terminal 910 and a timepoint of reception in the small cell base station 930.

In step 911, the macro base station 920 and the small cell base station930 coordinate resource allocation for the terminal 910. For this, themacro base station 920 and the small cell base station 930 may exchangeinformation of a required resource amount, an available resource amount,a position (e.g., frame, subframe, symbol/slot/sub channel position,etc.) of a resource to be actually allocated, etc. In detail, the macrobase station 920 and the small cell base station 930 determine a cellswitching time based on the switching delay time of the terminal 910 andTAs, and determine a resource empty of each cell in consideration of thecell switching time. The resource empty may be expressed by the unit offrame, subframe, slot, symbol, etc. For example, the resource empty maybe used to make empty a certain duration in the last subframe of macrobase station downlink, or in the first subframe of macro base stationuplink, or in the last subframe of small cell base station downlink, orin the first subframe of small cell base station uplink. In accordancewith one exemplary embodiment of the present invention, information onthe resource empty may be forwarded even to the terminal 910. Forexample, the information on the resource empty may be provided as a partof the resource allocation information provided to the terminal 910. Ifthe macro base station 920 and the small cell base station 930 arenetwork entities belonging to different systems, information providedbetween the macro base station 920 and the small cell base station 930may be transmitted after being processed into a form interpretable at areception side, or the reception side may have a capability capable ofinterpreting a format of a transmission side system. Or, a third entityfor processing of the information exists, and the third entity mayprocess and forward the information.

In step 913, the macro base station 920 allocates a resource for theterminal 910 in consideration of the cell switching time of the terminal910, a resource state, and transmits resource allocation information.

In step 915, the small cell base station 930 allocates a resource forthe terminal 910 in consideration of the cell switching time of theterminal 910, a resource state, and transmits resource allocationinformation. At this time, in case that the resource empty is set in aresource of the small cell base station 930, the small cell base station930 allocates a resource to the terminal 910 in the remnant regionexcepting the resource empty. For example, if the resource empty is twosubframes of an uplink region, the small cell base station 930 allocatesa resource to the terminal 910 in the remnant region excepting twosubframes of a front end of the uplink region.

By using resources as mentioned above, a terminal may performcommunication with each base station through switching. However, due towrong determination of a cell switching time, a change of TA, othererrors, etc., a situation in which a resource region allocated in eachcell conflicts may take place.

The conflict represents a case in which all of a first resourceallocated by a macro base station and a second resource allocated by asmall cell base station cannot be used due to the cell switching time ofthe terminal. For example, in case that some or all of the firstresource and the second resource are overlapped, the conflict may takeplace. Or, although the first resource and the second resource are notoverlapped, in case that a difference of time between a time point totransmit/receive a signal through the first resource and a time point totransmit/receive a signal through the second resource is less than thecell switching time, in other words, in case that a suitable resourceempty is not guaranteed, the conflict may take place.

For example, the conflict of the resource regions may be determined by afailure of transmission of uplink data to all or any one of the macrobase station and the small cell base station in the resource regionindicated by the resource allocation information of each of the macrobase station and the small cell base station. That is, the conflict maytake place in case that a time for switching of the terminal between thetwo base stations is determined too long or too short and thus theuplink resource allocation fails to reflect the cell switching time ofthe terminal. In detail, the conflict may be detected by failing toreceive a feedback about uplink data transmitted by the terminal orreceiving a NAK (Non-acknowledgement).

For another example, in case that the resource empty is notified to theterminal, the terminal may determine whether the resource regionallocated to the terminal indicated by the resource allocationinformation belongs within the resource empty. In this case, theterminal may expect, prior to observing successful reception ornon-reception of the uplink data, a conflict of the resource regions.

FIG. 10 illustrates a signal exchange for processing a conflict ofresource allocation in a wireless communication system according to anexemplary embodiment of the present invention.

Referring to the FIG. 10, in step 1001, the terminal 1010 receivesresource allocation information from the macro base station 1020 and, instep 1003, receives resource allocation information from the small cellbase station 1030. Thereafter, in step 1005, the terminal 1010 transmitsuplink data to the macro base station 1020 through a resource checked bythe resource allocation information. In step 1007, the terminal 1010transmits uplink data to the small cell base station 1030 through aresource checked by the resource allocation information.

In step 1009, the terminal 1010 recognizes that a conflict betweenresource regions allocated by the macro base station 1020 and the smallcell base station 1030 occurs. The conflict represents a case in whichall of the resource allocated by the macro base station 1020 and theresource allocated by the small cell base station 1030 cannot be useddue to a cell switching time of the terminal 1010. The conflict may bedetected by recognizing a failure of uplink data transmission, or bedetected by comparing a resource empty and an actually allocatedresource.

In step 1011, the terminal 1010 reports the occurrence of the conflictbetween the resource regions to the macro base station 1020. Accordinglyto this, the macro base station 1020 may recognize the conflict. Inaccordance with another exemplary embodiment of the present invention,the macro base station 1020 or the small cell base station 1030 maydirectly detect the conflict by recognizing that uplink data is notnormally received from the terminal 1010. That the uplink data is notnormally received represents a case of conflicting with uplink data fromother terminal or a case in which data is not received in a regionallocated to the terminal 1010.

In step 1013, the macro base station 1020 and the small cell basestation 1030 coordinate resource allocation for the terminal 1010. Forthis, the macro base station 1020 and the small cell base station 1030may exchange information of a required resource amount, an availableresource amount, a position (e.g., frame, subframe, symbol/slot/subchannel position, etc.) of a resource to be actually allocated, etc.Through this, the macro base station 1020 and the small cell basestation 1030 redetermine the cell switching time of the terminal 1010.To redetermine the cell switching time, the macro base station 1020 andthe small cell base station 1030 may further perform a procedure foracquiring at least one of a switching delay time with the terminal 1010,TA information. And, the macro base station 1020 and the small cell basestation 1030 again determine a resource empty on the basis of theredetermined cell switching time. In accordance with one exemplaryembodiment of the present invention, information on the resource emptymay be forwarded even to the terminal 1010. If the macro base station1020 and the small cell base station 1030 are network entities belongingto different systems, information provided between the macro basestation 1020 and the small cell base station 1030 may be transmittedafter being processed into a form interpretable at a reception side, orthe reception side may have a capability capable of interpreting aformat of a transmission side system. Or, a third entity for processingof the information exists, and the third entity may process and forwardthe information.

In step 1015, the macro base station 1020 allocates a resource for theterminal 1010 in consideration of the cell switching time of theterminal 1010, a resource state, and transmits resource allocationinformation.

In step 1017, the small cell base station 1030 allocates a resource forthe terminal 1010 in consideration of the cell switching time of theterminal 1010, a resource state, and transmits resource allocationinformation. At this time, in case that the resource empty is set in aresource of the small cell base station 1030, the small cell basestation 1030 allocates a resource to the terminal 1010 in the remnantregion excepting the resource empty. For example, if the resource emptyis two subframes of an uplink region, the small cell base station 1030allocates a resource to the terminal 1010 in the remnant regionexcepting two subframes of a front end of the uplink region.

FIG. 11 illustrates a signal exchange for resource use in a wirelesscommunication system according to a further exemplary embodiment of thepresent invention.

Referring to the FIG. 11, in step 1101, a terminal 1110 performs an RACHprocedure with a macro base station 1120 during an initial connectionprocedure. For example, the terminal 1110 selects a resource for randomaccess, and transmits a random access preamble, and then receives arandom access response from the macro base station 1120. Through theRACH procedure, the terminal 1110 and the macro base station 1120 mayacquire TA information on the macro base station 1120. For example, themacro base station 1120 estimates a transmission timing of the terminal1110 using the random access preamble, and transmits a TA commandrelated to a TA through the random access response.

In step 1103, the terminal 1110 transmits capability informationincluding a switching delay time to the macro base station 1120. Thecapability information may include information on other hardware,software capability besides the switching delay time. In accordance withanother exemplary embodiment of the present invention, the switchingdelay time may be forwarded through a separate procedure or a separatemessage.

In step 1105, if a small cell base station 1130 the terminal 1110 is toconnect is determined, the terminal 1110 performs an RACH procedure soas to connect to the small cell base station 1130. For example, theterminal 1110 selects a resource for random access, and transmits arandom access preamble, and then receives a random access response fromthe macro base station 1120. Through the RACH procedure, the terminal1110 and the macro base station 1120 may acquire TA information on thesmall cell base station 1130. For example, the small cell base station1130 estimates a transmission timing of the terminal 1110 using therandom access preamble, and transmits a TA command related to a TAthrough the random access response.

In step 1107, the terminal 1110 reports the TA information on the smallcell base station 1130 to the macro base station 1120. Here, the TAinformation may directly or indirectly express, by the unit of time,resource, etc., a difference of time between a time point oftransmission in the terminal 1110 and a time point of reception in thesmall cell base station 1130.

In step 1109, the macro base station 1120 determines a cell switchingtime based on a switching delay time of the terminal 1110 and TAs, anddetermines a resource empty on the basis of the cell switching time, andthen allocates a resource to the terminal 1110 in consideration of thecell switching time of the terminal 1110 and resource states of the twobase stations 1120, 1130. At this time, the macro base station 1120allocates even a resource of a small cell as well as a resource of themacro cell.

In step 1111, the macro base station 1120 provides a resource allocationresult to the small cell base station 1130. The resource allocationresult includes resource empty information. At this time, the resourceallocation result provided to the small cell base station 1130 mayinclude only an allocation result of the resource of the small cell. Inaccordance with one exemplary embodiment of the present invention, theresource empty information may be forwarded even to the terminal 1110.For example, the resource empty information may be provided as a part ofresource allocation information provided to the terminal 1110. If themacro base station 1120 and the small cell base station 1130 are networkentities belonging to different systems, information provided from themacro base station 1120 to the small cell base station 1130 may betransmitted after being processed into a form interpretable in the smallcell base station 1130, or the small cell base station 1130 may have acapability capable of interpreting a format of a system which the macrobase station 1120 belongs to. Or, a third entity for processing of theinformation exists, and the third entity may process and forward theinformation.

In step 1113, the macro base station 1120 transmits resource allocationinformation on the macro cell and the small cell to the terminal 1110.Thereafter, though not illustrated in the FIG. 11, the terminal 1110performs communication with the macro base station 1120 and the smallcell base station 1130 through a resource checked by the resourceallocation information.

FIG. 12 illustrates a signal exchange for resource use in a wirelesscommunication system according to a yet another exemplary embodiment ofthe present invention.

Referring to the FIG. 12, in step 1201, a terminal 1210 performs an RACHprocedure with a macro base station 1220 during an initial connectionprocedure. For example, the terminal 1210 selects a resource for randomaccess, and transmits a random access preamble, and then receives arandom access response from the macro base station 1220. Through theRACH procedure, the terminal 1210 and the macro base station 1220 mayacquire TA information on the macro base station 1220. For example, themacro base station 1220 estimates a transmission timing of the terminal1210 using the random access preamble, and transmits a TA commandrelated to a TA through the random access response.

In step 1203, the terminal 1210 transmits capability informationincluding a switching delay time to the macro base station 1220. Thecapability information may include information on other hardware,software capability besides the switching delay time. In accordance withanother exemplary embodiment of the present invention, the switchingdelay time may be forwarded through a separate procedure or a separatemessage.

In step 1205, if a small cell base station 1230 the terminal 1210 is toconnect is determined, the terminal 1210 performs an RACH procedure soas to connect to the small cell base station 1230. For example, theterminal 1210 selects a resource for random access, and transmits arandom access preamble, and then receives a random access response fromthe macro base station 1220. Through the RACH procedure, the terminal1210 and the macro base station 1220 may acquire TA information on thesmall cell base station 1230. For example, the small cell base station1230 estimates a transmission timing of the terminal 1210 using therandom access preamble, and transmits a TA command related to a TAthrough the random access response.

In step 1207, the small cell base station 1230 reports the TAinformation on the small cell base station 1230 to the macro basestation 1220. Here, the TA information may directly or indirectlyexpress, by the unit of time, resource, etc., a difference of timebetween a time point of transmission in the terminal 1210 and a timepoint of reception in the small cell base station 1230.

In step 1209, the macro base station 1220 determines a cell switchingtime based on a switching delay time of the terminal 1210 and TAs, anddetermines a resource empty on the basis of the cell switching time, andthen allocates a resource to the terminal 1210 in consideration of thecell switching time of the terminal 1210 and resource states of the twobase stations 1220, 1230. At this time, the macro base station 1220allocates even a resource of a small cell as well as a resource of themacro cell.

In step 1211, the macro base station 1220 provides a resource allocationresult to the small cell base station 1230. The resource allocationresult includes resource empty information. At this time, the resourceallocation result provided to the small cell base station 1230 mayinclude only an allocation result of the resource of the small cell. Inaccordance with one exemplary embodiment of the present invention, theresource empty information may be forwarded even to the terminal 1210.If the macro base station 1220 and the small cell base station 1230 arenetwork entities belonging to different systems, information providedfrom the macro base station 1220 to the small cell base station 1230 maybe transmitted after being processed into a form interpretable in thesmall cell base station 1230, or the small cell base station 1230 mayhave a capability capable of interpreting a format of a system which themacro base station 1220 belongs to. Or, a third entity for processing ofthe information exists, and the third entity may process and forward theinformation.

In step 1213, the macro base station 1220 transmits resource allocationinformation on the macro cell and the small cell to the terminal 1210.Thereafter, though not illustrated in the FIG. 12, the terminal 1210performs communication with the macro base station 1220 and the smallcell base station 1230 through a resource checked by the resourceallocation information.

Unlike the exemplary embodiments illustrated in the FIG. 11 and the FIG.12, resource allocation information for a terminal may be transmitted byeach of the macro cell and the small cell. In this case, the terminalshould monitor the macro cell and the small cell, although notperforming data transmission/reception with the macro cell or the smallcell.

However, in case that the terminal monitors while switching between themacro cell and the small cell, a situation in which the terminalunnecessarily switches to monitor resource allocation though notperforming communication with the base station may occur. Accordingly, aseparate indicator may be used in order for the terminal to monitorresource allocation information in the macro cell and the small cell.Exemplary embodiments related to the indication are described withreference to FIG. 13 below and FIG. 14 below.

FIG. 13 illustrates a signal exchange for resource allocation monitoringin a wireless communication system according to an exemplary embodimentof the present invention.

Referring to the FIG. 13, although not illustrated, a terminal 1310 isin a state of monitoring resource allocation information of a macro basestation 1320 while transmitting/receiving data.

In step 1301, the macro base station 1320 and a small cell base station1330 share a resource allocation result for the terminal 1310. That is,the macro base station 1320 and small cell base station 1330 exchangethe resource allocation result for the terminal 1310. Through this, themacro base station 1320 and the small cell base station 1330 maydetermine whether the terminal 1310 performs communication with themacro base station 1320, or whether it performs communication with thesmall cell base station 1330, or whether it performs communication withall of the two base stations 1320, 1330. The aforementioneddetermination about the communication counterpart of the terminal 1310may be carried out at the time of configuring the resource allocationinformation for the terminal 1310, and may be performed every schedulingtime or at an interval of a plurality of scheduling time in accordancewith a certain period. If the macro base station 1320 and the small cellbase station 1330 are network entities belonging to different systems,information provided between the macro base station 1320 and the smallcell base station 1330 may be transmitted after being processed into aform interpretable at a reception side, or the reception side may have acapability capable of interpreting a format of a transmission sidesystem. Or, a third entity for processing of the information exists, andthe third entity may process and forward the information.

In step 1303, the macro base station 1320 allocates a resource to theterminal 1310. At this time, the macro base station 1320 may consider acell switching time of the terminal 1310.

In step 1305, the macro base station 1320 transmits resource allocationinformation to the terminal 1310. At this time, the macro base station1320 determines a time point at which the small cell base station 1330is to transmit resource allocation information, and transmits resourceallocation information including a monitoring indicator indicating toreceive the resource allocation information of the small cell basestation 1330 to the terminal 1310. In accordance with another exemplaryembodiment of the present invention, the monitoring indicator may betransmitted through other message or separate signaling, not theresource allocation information.

In step 1307, the terminal 1310 switches to the small cell base station1330. In detail, the terminal 1310 changes an operation frequency of anRF (Radio Frequency) module from a frequency of the macro base station1320 to a frequency of the small cell base station 1330. Or, theterminal 1310 changes an operation channel of the RF module from achannel of the macro base station 1320 to a channel of the small cellbase station 1330. At this time, it is not required to release a logicalconnectivity between the terminal 1310 and the macro base station 1320.

In step 1309, the small cell base station 1330 allocates a resource tothe terminal 1310. At this time, the small cell base station 1330considers a cell switching time of the terminal 1310. That is, the smallcell base station 1330 allocates the resource in the remnant regionexcepting a resource empty for the terminal 1310.

In step 1311, the small cell base station 1330 transmits resourceallocation information to the terminal 1310. At this time, the resourceallocation information includes a monitoring indicator indicating tokeep receiving the resource allocation information of the small cellbase station 1330.

In step 1313, the small cell base station 1330 allocates a resource tothe terminal 1310. At this time, the small cell base station 1330considers a cell switching time of the terminal 1310. That is, the smallcell base station 1330 allocates the resource in the remnant regionexcepting a resource empty for the terminal 1310.

In step 1315, the small cell base station 1330 transmits resourceallocation information to the terminal 1310. At this time, the smallcell base station 1330 determines that a resource is to be allocatedfrom the macro base station 1320 to the terminal 1310, and transmitsresource allocation information including a monitoring indicatorindicating to keep receiving resource allocation information of themacro base station 1320. Although not illustrated in the FIG. 13, thesmall cell base station 1330 may exchange the resource allocationinformation with the macro base station 1320 in order to determine abase station to service the terminal 1310.

In step 1317, the terminal 1310 switches to the macro base station 1320.In detail, the terminal 1310 changes an operation frequency of an RFmodule from a frequency of the small cell base station 1330 to afrequency of the macro base station 1320. Or, the terminal 1310 changesan operation channel of the RF module from a channel of the small cellbase station 1330 to a channel of the macro base station 1320. At thistime, a logical connectivity between the terminal 1310 and the smallcell base station 1330 is not released. Accordingly to this, theterminal 1310 may monitor the resource allocation informationtransmitted by the macro base station 1320.

In case of some of the aforementioned exemplary embodiments, each basestation allocates a resource of its own cell, and transmits resourceallocation information. In contrast, in case of other some exemplaryembodiments, one base station allocates resources of all cells, andtransmits resource allocation information of all the cells. A scheme ofresource allocation and resource allocation information transmission maybe determined by backhaul latency.

The backhaul latency represents a time required for signal forwarding atcommunication through a backhaul link between base stations. In casethat a macro base station schedules a resource of a small cell basestation, the macro base station should acquire information on the smallcell base station. For example, information necessary for schedulingincludes an available resource amount of the small cell base station,the number of connected terminals, a channel state with a terminal whichshould be allocated a resource, a required communication quality (e.g.,a transmission quantity, an MCS level, etc.), a position of a resourceallocated to a terminal, etc.

Accordingly, if a time required for collect information necessary forscheduling for a terminal is too long, it is desirable that basestations each transmit resource allocation information. In case that thebase stations each transmit the resource allocation information, theterminal should monitor the plurality of base stations. If only one basestation intends to transmit resource allocation information in order toprevent this, the time required for the base station transmitting theresource allocation information to collect information necessary forscheduling from other base stations should not be long. Therefore, ifthe backhaul latency is long and thus the time required to collect theinformation necessary for the scheduling becomes long, it is desirablethat the base stations each transmit the resource allocationinformation. In contrast, if the backhaul latency is not long and thusthe time required to collect the information necessary for thescheduling is not long, one base station may collect the informationnecessary for the scheduling, and schedule all of its own resource andresources of other base stations, and then transmit the resourceallocation information to a terminal.

FIG. 14 illustrates a signal exchange for scheduling type determinationin a wireless communication system according to an exemplary embodimentof the present invention.

Referring to the FIG. 14, in step 1401, a macro base station 1420collects backhaul latency information with a small cell base station1430, so as to determine a base station to transmit resource allocationinformation for a terminal 1410. For example, the macro base station1420 transmits a test signal for a communication state test, andmeasures a response time to the test signal, thereby being capable ofmeasuring the backhaul latency. If the macro base station 1420 and thesmall cell base station 1430 are network entities belonging to differentsystems, information provided between the macro base station 1420 andthe small cell base station 1430 may be transmitted after beingprocessed into a form interpretable at a reception side, or thereception side may have a capability capable of interpreting a format ofa transmission side system. Or, a third entity for processing of theinformation exists, and the third entity may process and forward theinformation.

In step 1403, the macro base station 1420 and the small cell basestation 1430 determine a scheduling type for the terminal. Thescheduling type represents whether one base station transmits resourceallocation information of a plurality of cells, or whether base stationseach transmit. The scheduling type may be determined on the basis of thebackhaul latency between the macro base station 1420 and the small cellbase station 1430. In case of the present exemplary embodiment, a ‘crosscell scheduling’ scheme in which one base station transmits resourceallocation information is selected.

In step 1405, the macro base station 1420 indicates a resourceallocation information monitoring type to the terminal 1410. In otherwords, the macro base station 1420 transmits an indicator indicating thescheduling type determined in the step 1403, i.e., a cross cellscheduling indicator. The cross cell scheduling indicates to monitorresource allocation information from the macro base station 1420.Accordingly to this, at duration not transmitting/receiving a signal,the terminal 1410 may exclude cell switching for monitoring of resourceallocation information. The cross cell scheduling indicator may beincluded and transmitted in the resource allocation information, or betransmitted through an L2 (layer-2) message.

In step 1407, the macro base station 1420 allocates a resource to theterminal 1410. The macro base station 1420 allocates even a resource ofa small cell as well as a resource of the macro cell. For this, themacro base station 1420 may collect information on the small cell basestation 1430 necessary for scheduling the resource of the small cellthrough a backhaul link. At this time, the macro base station 1420considers a cell switching time of the terminal 1410.

In step 1409, the macro base station 1420 provides a resource allocationresult to the small cell base station 1430. The resource allocationresult includes information indicating a position and size of theresource allocated to the terminal 1410 among the resource of the smallcell, and may further include resource empty information. If the macrobase station 1420 and the small cell base station 1430 are networkentities belonging to different systems, information provided from themacro base station 1420 to the small cell base station 1430 may betransmitted after being processed into a form interpretable in the smallcell base station 1430, or the small cell base station 1430 may have acapability capable of interpreting a format of a system which the macrobase station 1420 belongs to. Or, a third entity for processing of theinformation exists, and the third entity may process and forward theinformation.

In step 1411, the macro base station 1420 transmits resource allocationinformation on the macro cell and the small cell to the terminal 1410.Thereafter, although not illustrated in the FIG. 14, the macro basestation 1420 and the small cell base station 1430 continuously observebackhaul latency information, and determine whether the scheduling typeof the terminal 1410 should be changed in accordance with a change ofthe backhaul latency.

FIG. 15 illustrates a signal exchange for scheduling type determinationin a wireless communication system according to another exemplaryembodiment of the present invention.

Referring to the FIG. 15, in step 1501, a macro base station 1520collects backhaul latency information with a small cell base station1530, in order to determine a base station to transmit resourceallocation information for a terminal 1510. For example, the macro basestation 1520 transmits a test signal for a communication state test, andmeasures a response time to the test signal, thereby being capable ofmeasuring the backhaul latency. If the macro base station 1520 and thesmall cell base station 1530 are network entities belonging to differentsystems, information provided between the macro base station 1520 andthe small cell base station 1530 may be transmitted after beingprocessed into a form interpretable at a reception side, or thereception side may have a capability capable of interpreting a format ofa transmission side system. Or, a third entity for processing of theinformation exists, and the third entity may process and forward theinformation.

In step 1503, the macro base station 1520 and the small cell basestation 1530 determine a scheduling type for the terminal. Here, thescheduling type represents whether one base station transmits resourceallocation information of a plurality of cells, or whether base stationseach transmit. The scheduling type may be determined on the basis ofbackhaul latency between the macro base station 1520 and the small cellbase station 1530. In case of the present exemplary embodiment, a ‘crosscell scheduling’ scheme in which one base station transmits resourceallocation information is selected.

In step 1505, the macro base station 1520 indicates a resourceallocation information monitoring type to the terminal 1510. In otherwords, the macro base station 1520 transmits an indicator indicating thescheduling type determined in the step 1503, i.e., an individual cellscheduling indicator. The individual cell scheduling indicates tomonitor resource allocation information from the macro base station 1520and resource allocation information from the small cell base station1530. The individual cell scheduling indicator may be included andtransmitted in the resource allocation information, or be transmittedthrough an L2 message.

In step 1507, the macro base station 1520 allocates a resource to theterminal 1510. The macro base station 1520 allocates a resource of themacro cell. At this time, the macro base station 1520 considers a cellswitching time of the terminal 1510.

In step 1509, the small cell base station 1530 allocates a resource tothe terminal 1510. The small cell base station 1530 allocates a resourceof the small cell. At this time, the small cell base station 1530considers a cell switching time of the terminal 1510.

In step 1511, the macro base station 1520 transmits resource allocationinformation on the macro cell to the terminal 1510. In step 1513, thesmall cell base station 1530 transmits resource allocation informationon the small cell to the terminal 1510. Thereafter, although notillustrated in the FIG. 15, the macro base station 1520 and the smallcell base station 1530 continuously observe backhaul latencyinformation, and determine whether the scheduling type of the terminal1510 should be changed in accordance with a change of the backhaullatency.

FIG. 16 illustrates an operation procedure of a terminal in a wirelesscommunication system according to an exemplary embodiment of the presentinvention.

Referring to the FIG. 16, in step 1601, the terminal initiates aninitial connection procedure through a macro base station, and performsan RACH procedure with the macro base station. Through the RACHprocedure, the terminal may acquire TA information on the macro basestation.

After performing the RACH procedure, the terminal proceeds to step 1603and transmits a switching delay time of the terminal to the macro basestation. The switching delay time may be transmitted as a part ofcapability information of the terminal. The capability information mayinclude information on other hardware, software capability besides theswitching delay time. In accordance with another exemplary embodiment ofthe present invention, the switching delay time may be forwarded througha separate procedure or a separate message.

Thereafter, the terminal proceeds to step 1605 and determines if aconnectivity to a small cell base station is indicated by the macro basestation. The connectivity to the small cell base station is indicated incase that it is determined that the small cell base station is toservice the terminal. Service provision or non-provision of the smallcell base station may be determined by the macro base station on thebasis of a wireless channel quality of the terminal, a network resourcepresent condition, etc.

If the connectivity to the small cell base station is not indicated fromthe macro base station, the terminal proceeds to step 1607 and performscommunication with the macro base station. That is, the terminalreceives resource allocation information from the macro base station,receives a downlink signal through an allocated resource, and transmitsan uplink signal.

In contrast, if the connectivity to the small cell base station isindicated from the macro base station, the terminal proceeds to step1609 and performs an RACH procedure with the small cell base station.Through the RACH procedure, the terminal may acquire TA information onthe small cell base station.

Next, the terminal proceeds to step 1611 and transmits TA information tothe macro base station and the small cell base station. At this time,the terminal transmits the TA information on the small cell base stationto the macro base station, the TA information on the macro base stationto the small cell base station. The TA information may directly orindirectly express, by the unit of time, resource, etc., a difference oftime between a time point of transmission in the terminal and a timepoint of reception in the macro base station. However, in accordancewith another exemplary embodiment of the present invention, the step1611 may be omitted. In this case, the macro base station and the smallcell base station mutually exchange the TA information.

Next, the terminal proceeds to step 1613 and reports a switching delaytime of the terminal to the small cell base station. The switching delaytime may be transmitted as a part of capability information of theterminal. However, in accordance with another exemplary embodiment ofthe present invention, the step 1613 may be omitted. In this case, themacro base station provides switching delay time information of theterminal to the small cell base station.

Thereafter, the terminal proceeds to step 1615 and performscommunication with the macro base station and the small cell basestation. That is, the terminal receives resource allocation informationof the macro base station and the small cell base station, and performscommunication with the macro base station and the small cell basestation in accordance with the resource allocation information. Here,the resource allocation information may be received from each of themacro base station and the small cell base station, or be received fromthe macro base station only. The resource allocation informationincludes information indicating a position and size of a resourceallocated to the terminal, and may further include at least one of aresource empty, a CP (Cyclic Prefix) length, a scheduling typeindicator, a monitoring indicator. In case that performing thecommunication with the macro base station and the small cell basestation, the terminal may perform cell switching according to cases.

FIG. 17 illustrates an operation procedure of a terminal in a wirelesscommunication system according to another exemplary embodiment of thepresent invention.

Referring to the FIG. 17, in step 1701, the terminal performscommunication with a macro base station and a small cell base station.That is, the terminal receives resource allocation information of themacro base station and the small cell base station, and performscommunication with the macro base station and the small cell basestation in accordance with the resource allocation information.According to cases, the terminal may perform cell switching.

While performing the communication, the terminal proceeds to step 1703and determines if a conflict between resource regions of the macro basestation and the small cell base station allocated to the terminaloccurs. For example, the terminal recognizes a failure of uplink datatransmission or compares a resource empty and an actually allocatedresource, thereby being capable of detecting the conflict.

In case that the conflict occurs, the terminal proceeds to step 1705 andreports, to the macro base station, the occurrence of the conflict. Forexample, the terminal transmits a separate message, signal sequencedefined for the conflict report. The terminal may transmit the signalsequence through a feedback channel.

Thereafter, the terminal returns to the step 1701 and performscommunication. At this time, although not illustrated in the FIG. 17,the terminal may receive changed resource allocation information fromthe macro base station. The resource allocation information includesinformation indicating a position and size of a resource allocated tothe terminal, and may further include at least one of a resource empty,a CP length, a scheduling type indicator, a monitoring indicator.

FIG. 18 illustrates an operation procedure of a terminal in a wirelesscommunication system according to a further exemplary embodiment of thepresent invention.

Referring to the FIG. 18, in step 1801, the terminal performscommunication with a macro base station and a small cell base station.That is, the terminal receives resource allocation information of themacro base station and the small cell base station, and performscommunication with the macro base station and the small cell basestation in accordance with the resource allocation information.According to cases, the terminal may perform cell switching.

While performing the communication, the terminal proceeds to step 1803and determines if a TA for the macro base station or the small cell basestation is changed. The TA may be changed as a distance with the macrobase station or small cell base station is changed according to movementof the terminal.

If the TA for the macro base station or small cell base station ischanged, the terminal proceeds to step 1805 and transmits the changed TAinformation to a corresponding base station. The changed TA informationmay express the changed TA itself, or express a difference value withprevious TA. However, in accordance with another exemplary embodiment ofthe present invention, although the TA is changed, the terminal may nottransmit the changed TA information. In this case, the changed TAinformation may be directly exchanged between the macro base station andthe small cell base station.

Thereafter, the terminal returns to the step 1801 and performscommunication. At this time, although not illustrated in the FIG. 18,the terminal may receive resource allocation information from at leastone of the macro base station and the small cell base station. Theresource allocation information includes information indicating aposition and size of a resource allocated to the terminal, and mayfurther include at least one of a resource empty, a CP length, ascheduling type indicator, a monitoring indicator.

FIG. 19 illustrates an operation procedure of a terminal in a wirelesscommunication system according to a yet another exemplary embodiment ofthe present invention.

Referring to the FIG. 19, in step 1901, the terminal receives amonitoring related indicator. The indicator may indicate at least one ofneed or non-need of cell switching for monitoring, a scheduling type.The scheduling type represents whether one base station transmitsresource allocation information of a plurality of cells, or whether basestations each transmit. The indicator may be received together withresource allocation information.

After receiving the indicator, the terminal proceeds to step 1903 anddetermines execution or non-execution of cell switching for resourceallocation information monitoring. For example, in case that theindicator indicates that a macro base station transmits resourceallocation information of a plurality of cells, the terminal monitorsresource allocation information of the macro base station, anddetermines to exclude the cell switching. For another example, in casethat the indicator indicates that base stations each transmit theresource allocation information of the plurality of cells, the terminaldetermines to perform the cell switching so as to monitor resourceallocation information transmitted by each of the base stations. At thistime, the terminal may perform the cell switching in accordance with anindicator indicating that there is a need for the cell switching. Thatis, if the indicator indicates that there is not the need for the cellswitching, the terminal may exclude the cell switching, although aresource allocation information transmission time point of other basestation arrives.

FIG. 20 illustrates an operation procedure of a macro base station in awireless communication system according to an exemplary embodiment ofthe present invention.

Referring to the FIG. 20, in step 2001, the macro base station performsan RACH procedure with a terminal which performs an initial entryprocedure. Through the RACH procedure, the macro base station mayacquire TA information of the terminal.

After performing the RACH procedure, the macro base station proceeds tostep 2003 and receives switching delay time information of the terminalfrom the terminal. The switching delay time information may be receivedas a part of capability information of the terminal. The capabilityinformation may include information on other hardware, softwarecapability besides the switching delay time. In accordance with anotherexemplary embodiment of the present invention, the switching delay timemay be forwarded through a separate procedure or a separate message.

Thereafter, the macro base station proceeds to step 2005 and determineswhether to service the terminal together with a small cell base station.Service provision or non-provision of the small cell base station may bedetermined on the basis of a wireless channel quality of the terminal, anetwork resource present condition, etc. Also, the service provision ornon-provision of the small cell base station may be determined in casethat there is a request of the terminal. If it is determined not toservice together with the small cell base station, the macro basestation proceeds to step 2013 below.

In contrast, if it is determined to service together with the small cellbase station, the macro base station proceeds to step 2007 and provides,to the small cell base station, a switching delay time of the terminaland TA information on the macro base station of the terminal. The TAinformation may directly or indirectly express, by the unit of time,resource, etc., a difference of time between a time point oftransmission in the terminal and a time point of reception in the macrobase station. However, in accordance with another exemplary embodimentof the present invention, the TA information of the terminal may not beprovided by the small cell base station. In this case, the TAinformation on the macro base station is provided to the small cell basestation by the terminal.

Thereafter, the macro base station proceeds to step 2009 and receives TAinformation on the small cell base station of the terminal. The TAinformation may directly or indirectly express, by the unit of time,resource, etc., a difference of time between a time point oftransmission in the terminal and a time point of reception in the smallcell base station. However, in accordance with an exemplary embodimentof the present invention, the TA information on the small cell basestation may be provided from the small cell base station. In accordancewith another exemplary embodiment of the present invention, the TAinformation on the small cell base station may be provided from theterminal.

Next, the macro base station proceeds to step 2011 and coordinatesresource allocation for the terminal with the small cell base station.For this, the macro base station and the small cell base station mayexchange information of a required resource amount, an availableresource amount, a position of an actually allocated resource, etc. Indetail, the macro base station determines a cell switching time of theterminal. The cell switching time is determined on the basis of aswitching delay time of the terminal and TAs. And, the macro basestation determines a resource empty for the terminal.

Thereafter, the macro base station proceeds to step 2013 and allocates aresource to the terminal, and transmits resource allocation information.At this time, in accordance with a scheduling type, the macro basestation may allocate only a resource of a macro cell, or allocate all ofthe resource of the macro cell and a resource of a small cell. In casethat allocating even the resource of the small cell, the macro basestation may collect information of the small cell base station necessaryfor scheduling through a backhaul link.

After transmission of the resource allocation information, the macrobase station proceeds to step 2015 and performs communication with theterminal. That is, the macro base station transmits a downlink signaland receives an uplink signal, through the resource of the macro cellallocated to the terminal.

FIG. 21 illustrates an operation procedure of a macro base station in awireless communication system according to another exemplary embodimentof the present invention.

Referring to the FIG. 21, in step 2101, the macro base station performscommunication with a terminal. That is, the macro base station allocatesa resource to the terminal, and transmits a downlink signal and receivesan uplink signal, through the allocated resource.

While performing the communication with the terminal, the macro basestation proceeds to step 2103 and determines if a conflict occursbetween resource regions of the macro base station and a small cell basestation allocated to the terminal. The occurrence or non-occurrence ofthe conflict may be determined by a report of the terminal. Inaccordance with another exemplary embodiment, the conflict may bedirectly determined by the macro base station. For example, theoccurrence of the conflict may be determined in case that a failure ofuplink data reception from the terminal through the resource allocatedto the terminal, or a failure of downlink data transmission to theterminal is recognized. Here, the downlink data transmission failure maybe recognized by failing to receive a feedback about the downlink data,or receiving a NAK. If the resource conflict does not occur, the macrobase station returns to the step 2101 and performs communication withthe terminal.

In contrast, if the conflict occurs, the macro base station proceeds tostep 2105 and recoordinates resource allocation for the terminal. Thatis, the macro base station redetermines a cell switching time of theterminal, and redetermines a resource empty on the basis of the cellswitching time. For this, the macro base station may exchange necessaryinformation with the small cell base station. The necessary informationmay include at least one of TA information of the terminal, a resourcestate of the small cell base station so as to redetermine the cellswitching time of the terminal.

After that, the macro base station returns to the step 2101 and performscommunication with the terminal. At this time, though not illustrated inthe FIG. 21, the macro base station may allocate a resource to theterminal based on the redetermined cell switching time of the terminal,and transmit resource allocation information. The resource allocationinformation includes information indicating a position and size of aresource allocated to the terminal, and may further include at least oneof a resource empty, a CP length, a scheduling type indicator, amonitoring indicator. In case that performing communication with themacro base station and the small cell base station, the terminal mayperform cell switching according to cases.

FIG. 22 illustrates an operation procedure of a macro base station in awireless communication system according to a further exemplaryembodiment of the present invention.

Referring to the FIG. 22, in step 2201, the macro base station performscommunication with a terminal. That is, the macro base station allocatesa resource to the terminal, and transmits a downlink signal and receivesan uplink signal through the allocated resource.

While performing the communication with the terminal, the macro basestation proceeds to step 2203 and determines if a TA for the macro basestation or a small cell base station of the terminal is changed. Thechange of the TA may be determined according to a report of theterminal. If the TA is not changed, the macro base station returns tothe step 2201 and performs communication with the terminal.

In contrast, if the TA is changed, the macro base station proceeds tostep 2205 and recoordinates resource allocation for the terminal. Forthis, the macro base station exchanges necessary information with thesmall cell base station. The necessary information may include at leastone of changed TA information of the terminal, a resource state of thesmall cell base station so as to redetermine the cell switching time ofthe terminal. That is, after acquiring the changed TA information, themacro base station redetermines the cell switching time of the terminal.And, the macro base station recoordinates the resource allocation of theterminal on the basis of the redetermined cell switching time.

After that, the macro base station returns to the step 2201 and performscommunication with the terminal. At this time, although not illustratedin the FIG. 22, the macro base station may allocate a resource to theterminal based on the redetermined cell switching time of the terminal,and transmit resource allocation information. The resource allocationinformation includes information indicating a position and size of theresource allocated to the terminal, and may further include at least oneof a resource empty, a CP length, a scheduling type indicator, amonitoring indicator. In case that performing communication with themacro base station and the small cell base station, the terminal mayperform cell switching according to cases.

FIG. 23 illustrates an operation procedure of a small cell base stationin a wireless communication system according to an exemplary embodimentof the present invention. The small cell base station may be a networkentity belonging to the same system as that of a macro base station, ora network entity belonging to a different system.

Referring to the FIG. 23, in step 2301, the small cell base stationreceives information on a terminal from the macro base station. Theinformation on the terminal includes at least one of a switching delaytime, TA information on the macro base station of the terminal. The TAinformation may directly or indirectly express, by the unit of time,resource, etc., a difference of time between a time point oftransmission in the terminal and a time point of reception in the macrobase station. In accordance with another exemplary embodiment of thepresent invention, the TA information may be received from the terminal,not the macro base station. Also, in accordance with a further exemplaryembodiment of the present invention, the switching delay time may bealso received from the terminal, not the macro base station. In thiscase, the switching delay time may be received as a part of capabilityinformation of the terminal.

Thereafter, the small cell base station proceeds to step 2303 andperforms an RACH procedure with the terminal. Through the RACHprocedure, the small cell base station may acquire TA information on thesmall cell base station of the terminal.

Although not illustrated in the FIG. 23, after performing the RACHprocedure, the small cell base station may receive the switching delaytime from the terminal. In this case, the switching delay time may notbe included in the information on the terminal received in the step2301. That is, if the switching delay time is included in theinformation on the terminal received in the step 2301, step of receivingthe switching delay time is omitted.

Thereafter, the small cell base station proceeds to step 2305 andcoordinates resource allocation for the terminal with the macro basestation. For this, the macro base station and the small cell basestation may exchange information of a required resource amount, anavailable resource amount, a position of an actually allocated resource,etc. In detail, the small cell base station determines a cell switchingtime of the terminal. The cell switching time is determined on the basisof a switching delay time of the terminal and TAs. In accordance withanother exemplary embodiment of the present invention, the cellswitching time may be determined by the macro base station and then, beprovided to the small cell base station. And, the small cell basestation determines a resource empty for the terminal. In accordance withanother exemplary embodiment of the present invention, the resourceempty may be determined by the macro base station and then, be providedto the small cell base station.

Thereafter, the small cell base station proceeds to step 2307 andperforms communication with the terminal. At this time, in accordancewith a scheduling type, the small cell base station may directlyallocate a resource of a small cell, or follow a resource allocationresult provided from the macro base station. In case that the resourceof the small cell is allocated by the macro base station, the small cellbase station may provide information of the small cell base stationnecessary for scheduling through a backhaul link. And, the small cellbase station transmits a downlink signal and receives an uplink signal,through the small cell resource allocated to the terminal.

Although not illustrated in the FIG. 23, in case that a conflict betweena resource region of a macro base station allocated to a terminal and aresource region of a small cell base station in course of communicationwith the terminal is determined, the small cell base station may reportthe resource conflict of the terminal to the macro base station. Forexample, in case that failing to normally receive uplink data from theterminal or failing to normally receive a feedback about downlink datatransmitted to the terminal, the small cell base station may determinethe occurrence of the conflict.

FIG. 24 illustrates a block construction of a terminal in a wirelesscommunication system according to an exemplary embodiment of the presentinvention.

Referring to the FIG. 24, the terminal includes an RF processor 2410, abaseband processor 2420, a storage unit 2430, and a controller 2440.

The RF processor 2410 performs a function for transmitting/receiving asignal through a wireless channel such as signal band conversion,amplification, etc. That is, the RF processor 2410 up converts abaseband signal provided from the baseband processor 2420 into an RFband signal and then transmits through an antenna, and down converts anRF band signal received through the antenna into a baseband signal. Forexample, the RF processor 2410 may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, a DAC (Digitalto Analog Converter), an ADC (Analog to Digital Converter), etc. In theFIG. 24, only one antenna is illustrated, but the terminal may have aplurality of antennas. Also, the RF processor 2410 may include aplurality of RF chains.

The baseband processor 2420 performs a function of conversion between abaseband signal and a bit stream according to the physical layerstandard of the system. For example, at data transmission, the basebandprocessor 2420 creates complex symbols by encoding and modulating atransmission bit stream. Also, at data reception, the baseband processor2420 restores a reception bit stream through demodulation and decodingof a baseband signal provided from the RF processor 2410. For example,according to an OFDM (Orthogonal Frequency Division Multiplexing)scheme, at data transmission, the baseband processor 2420 createscomplex symbols by encoding and modulating a transmission bit stream,and maps the complex symbols to subcarriers, and then constructs OFDMsymbols through IFFT (Inverse Fast Fourier Transform) operation and CPinsertion. Also, at data reception, the baseband processor 2420 dividesa baseband signal provided from the RF processor 2410 by the unit ofOFDM symbol, and restores signals mapped to subcarriers through FFT(Fast Fourier Transform) operation, and then restores a reception bitstream through demodulation and decoding. The baseband processor 2420and the RF processor 2410 transmit and receive a signal as mentionedabove. Accordingly to this, the baseband processor 2420 and the RFprocessor 2410 may be called a transmission unit, a reception unit, or atransmission/reception unit.

The storage unit 2430 stores data of a basic program for an operation ofthe terminal, an application program, setting information, etc. And, thestorage unit 2430 provides the stored data in accordance with a requestof the controller 2440.

The controller 2440 controls general operations of the terminal. Forexample, the controller 2440 transmits/receives a signal through thebaseband processor 2420 and the RF processor 2410. In accordance with anexemplary embodiment of the present invention, the controller 2440includes a switching controller 2442 performing switching between cells,and a conflict manager 2444 recognizing and reporting a conflict betweenresource regions. For example, the controller 2440 controls the terminalto operate like the terminals illustrated in the FIG. 8 to the FIG. 15,and perform the procedures illustrated in the FIG. 16 to the FIG. 19. Anoperation of the controller 2440 according to an exemplary embodiment ofthe present invention is given as follows.

In accordance with one exemplary embodiment of the present invention,the controller 2440 acquires TA information on a macro base stationthrough an RACH procedure with the macro base station and then,transmits a switching delay time of the terminal to the macro basestation. Thereafter, if a connectivity to a small cell base station isindicated from the macro base station, the controller 2440 performs aconnection procedure with the small cell base station. At this time, thecontroller 2440 acquires TA information on the small cell base stationthrough the RACH procedure, and transmits the TA information to themacro base station and the small cell base station. However, inaccordance with another exemplary embodiment of the present invention,the macro base station and the small cell base station may mutuallyexchange the TA information and, in this case, the TA informationtransmission is omitted. And, the controller 2440 reports a switchingdelay time of the terminal to the small cell base station. However, inaccordance with another exemplary embodiment of the present invention,the macro base station may provide switching delay time information ofthe terminal to the small cell base station. In this case, the report ofthe switching delay time is omitted. Thereafter, the controller 2440controls to perform communication with the macro base station and thesmall cell base station through an allocated resource. At this time, theresource allocation information may be received from each of the macrobase station and the small cell base station, or be received from themacro base station only.

In accordance with another exemplary embodiment of the presentinvention, while performing communication with a macro base station anda small cell base station, the controller 2440 determines if a conflictbetween resource regions of the macro base station and the small cellbase station allocated to the terminal occurs. For example, thecontroller 2440 recognizes a failure of uplink data transmission orcompares a resource empty and an actually allocated resource, therebybeing capable of detecting the conflict. In case that the conflictoccurs, the controller 2440 reports, to the macro base station, theoccurrence of the conflict. For example, the controller 2440 transmits aseparate message, signal sequence defined for the conflict report.

In accordance with a further exemplary embodiment of the presentinvention, while performing communication with a macro base station anda small cell base station, the controller 2440 determines if a TA forthe macro base station or the small cell base station is changed. The TAmay be changed as a distance with the macro base station or small cellbase station is changed according to movement of the terminal. If the TAfor the macro base station or small cell base station is changed, thecontroller 2440 transmits the changed TA information to a correspondingbase station. The changed TA information may express the changed TAitself, or express a difference value with previous TA. However, inaccordance with another exemplary embodiment of the present invention,although the TA is changed, the controller 2440 may not transmit thechanged TA information. In this case, the changed TA information may bedirectly exchanged between the macro base station and the small cellbase station.

In accordance with a yet another exemplary embodiment of the presentinvention, the controller 2440 receives a monitoring related indicator.The indicator may indicate at least one of need or non-need of cellswitching for monitoring, a scheduling type. The scheduling typerepresents whether one base station transmits resource allocationinformation of a plurality of cells, or whether base stations eachtransmit. The indicator may be received together with resourceallocation information.

After receiving the indicator, the controller 2440 determines executionor non-execution of cell switching for resource allocation informationmonitoring. For example, in case that the indicator indicates that amacro base station transmits resource allocation information of aplurality of cells, the controller 2440 monitors resource allocationinformation of the macro base station, and determines to exclude thecell switching. For another example, in case that the indicatorindicates that base stations each transmit the resource allocationinformation of the plurality of cells, the controller 2440 determines toperform cell switching in order to monitor resource allocationinformation transmitted by each of the base stations. At this time, thecontroller 2440 may perform the cell switching in accordance with anindicator indicating that there is a need for the cell switching. Thatis, if the indicator indicates that there is not the need for the cellswitching, the controller 2440 may exclude the cell switching, althougha resource allocation information transmission time point of other basestation arrives.

FIG. 25 illustrates a block construction of a base station in a wirelesscommunication system according to an exemplary embodiment of the presentinvention.

Referring to the FIG. 25, the base station includes an RF processor2510, a baseband processor 2520, a backhaul communication unit 2530, astorage unit 2540, and a controller 2550.

The RF processor 2510 performs a function for transmitting/receiving asignal through a wireless channel such as signal band conversion,amplification, etc. That is, the RF processor 2510 up converts abaseband signal provided from the baseband processor 2520 into an RFband signal and then transmits through an antenna, and down converts anRF band signal received through the antenna into a baseband signal. TheRF processor 2510 includes RF chains for each of a plurality ofantennas, and each RF chain may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,etc.

The baseband processor 2520 performs a function of conversion between abaseband signal and a bit stream according to the physical layerstandard of the system. For example, according to an OFDM scheme, atdata transmission, the baseband processor 2520 creates complex symbolsby encoding and modulating a transmission bit stream, and maps thecomplex symbols to subcarriers, and then constructs OFDM symbols throughIFFT operation and CP insertion. Also, at data reception, the basebandprocessor 2520 divides a baseband signal provided from the RF processor2510 by the unit of OFDM symbol, and restores signals mapped tosubcarriers through FFT operation, and then restores a reception bitstream through demodulation and decoding. The baseband processor 2520and the RF processor 2510 transmit and receive a signal as mentionedabove. Accordingly to this, the baseband processor 2520 and the RFprocessor 2510 may be called a transmission unit, a reception unit, or atransmission/reception unit.

The backhaul communication unit 2530 provides an interface forperforming communication with other nodes within a network such as otherbase stations, etc. That is, the backhaul communication unit 2530converts, into a physical signal, a bit stream transmitted from the basestation to other node, for example, other base station, a core network,etc., and converts a physical signal received from the other node into abit stream. The storage unit 2540 stores data of a basic program for anoperation of the base station, an application program, settinginformation, etc. And, the storage unit 2540 provides the stored data inaccordance with a request of the controller 2550.

The controller 2550 controls general operations of the base station. Forexample, the controller 2550 transmits/receives a signal through thebaseband processor 2520 or the RF processor 2510 or through the backhaulcommunication unit 2530. Also, the controller 2550 records data in thestorage unit 2540, and reads. In accordance with an exemplary embodimentof the present invention, the controller 2550 includes a resourcecoordination unit 2552 coordinating resource allocation for the terminalsuch as determining a cell switching time of the terminal, determining aresource empty on the basis of the cell switching time, etc. Forexample, the controller 2550 controls the base station to operate likethe macro base station or the small cell base station illustrated in theFIG. 8 to the FIG. 15, and perform the procedures illustrated in theFIG. 20 to the FIG. 23. An operation of the controller 2550 according toan exemplary embodiment of the present invention is given as follows.

First, a description is made for a case in which the base station is amacro base station.

Referring to the FIG. 20, the controller 2550 acquires TA information ofa terminal through an RACH procedure with the terminal which performs aninitial entry procedure, and receives switching delay time informationof the terminal from the terminal. If it is determined to service theterminal together with a small cell base station, the controller 2550provides, to the small cell base station, a switching delay time of theterminal and TA information on the macro base station of the terminal.However, in accordance with another exemplary embodiment of the presentinvention, the TA information on the macro base station may be providedto the small cell base station by the terminal and, in this case, theprovision of the TA information between the base stations is omitted.Thereafter, the controller 2550 receives TA information on the smallcell base station of the terminal. In accordance with an exemplaryembodiment of the present invention, the TA information on the smallcell base station may be provided from the small cell base station.Next, the controller 2550 coordinates resource allocation for theterminal with the small cell base station. For this, the macro basestation and the small cell base station may exchange information of arequired resource amount, an available resource amount, a position of anactually allocated resource, etc. In detail, the controller 2550determines a cell switching time of the terminal, and determines aresource empty for the terminal. Thereafter, the controller 2550allocates a resource to the terminal, and transmits resource allocationinformation. At this time, in accordance with a scheduling type, thecontroller 2550 may allocate only a resource of a macro cell, orallocate all of the resource of the macro cell and a resource of a smallcell. In case that allocating even the resource of the small cell, thecontroller 2550 may collect information of the small cell base stationnecessary for scheduling through a backhaul link.

In accordance with another exemplary embodiment of the presentinvention, while performing communication with the terminal, thecontroller 2550 determines if a conflict between resource regions of themacro base station and small cell base station allocated to the terminaloccurs. The occurrence or non-occurrence of the conflict may bedetermined by a report of the terminal. In accordance with anotherexemplary embodiment, the conflict may be directly determined by themacro base station. If the conflict occurs, the controller 2550recoordinates resource allocation for the terminal. That is, thecontroller 2550 redetermines a cell switching time of the terminal, andredetermines a resource empty on the basis of the cell switching time.For this, the controller 2550 may exchange necessary information withthe small cell base station. The necessary information may include atleast one of TA information of the terminal, a resource state of thesmall cell base station so as to redetermine the cell switching time ofthe terminal.

In accordance with a further exemplary embodiment of the presentinvention, while performing communication with the terminal, thecontroller 2550 determines if a TA for the macro base station or smallcell base station of the terminal is changed. The change of the TA maybe determined according to a report of the terminal. If the TA ischanged, the controller 2550 recoordinates resource allocation for theterminal. For this, the controller 2550 exchanges necessary informationwith the small cell base station. The necessary information may includeat least one of changed TA information of the terminal, a resource stateof the small cell base station so as to redetermine the cell switchingtime of the terminal. That is, after acquiring the changed TAinformation, the controller 2550 redetermines a cell switching time ofthe terminal. And, the controller 2550 recoordinates resource allocationof the terminal on the basis of the redetermined cell switching time.

Next, a description is made for a case in which the base station is asmall cell base station.

In accordance with an exemplary embodiment of the present invention, thecontroller 2550 receives information on a terminal, for example, atleast one of a switching delay time of the terminal, TA information on amacro base station of the terminal from the macro base station. Inaccordance with another exemplary embodiment of the present invention,the TA information may be received from the terminal, not the macro basestation. Also, in accordance with a further exemplary embodiment of thepresent invention, the switching delay time may be also received fromthe terminal, not the macro base station. Thereafter, the controller2550 performs an RACH procedure with the terminal and, through the RACHprocedure, the controller 2550 acquires TA information on the small cellbase station of the terminal. Thereafter, the controller 2550coordinates resource allocation for the terminal with the macro basestation. For this, the macro base station and the controller 2550 mayexchange information of a required resource amount, an availableresource amount, a position of an actually allocated resource, etc.Thereafter, the controller 2550 controls to perform communication withthe terminal. At this time, in accordance with a scheduling type, thecontroller 2550 may directly allocate a resource of a small cell, orfollow a resource allocation result provided from the macro basestation. In case that the resource of the small cell is allocated by themacro base station, the controller 2550 may provide information of thesmall cell base station necessary for scheduling through a backhaullink. And, the controller 2550 transmits a downlink signal and receivesan uplink signal, through the small cell resource allocated to theterminal.

In accordance with another exemplary embodiment of the presentinvention, in case that a conflict between a resource region of a macrobase station allocated to a terminal and a resource region of a smallcell base station in course of communication with the terminal isdetermined, the controller 2550 may report the resource conflict of theterminal to the macro base station through the backhaul communicationunit 2540.

The aforementioned exemplary embodiments of the present invention makeempty some resources of a macro base station or a small cell basestation on the basis of a cell switching time of a terminal. Inaccordance with another exemplary embodiment of the present invention,the macro base station and the small cell base station may applydifferent CP lengths on the basis of the cell switching time of theterminal. For example, in case that the cell switching time determinedon the basis of a switching delay time of the terminal and TAs gets outof a CP length generally applying in a system, a CP having a lengthequal to or greater than the cell switching time of the terminal may beapplied. At this time, the terminal may indicate to use other CPlengths.

Methods according to exemplary embodiments mentioned in claims and/orspecification of the present invention may be implemented in a form ofhardware, software, or a combination of the hardware and the software.

If the methods are implemented by the software, a computer-readablestorage medium storing one or more programs (software modules) may beprovided. The one or more programs stored in the computer-readablestorage medium are configured to be executed by one or more processorswithin an electronic device. The one or more programs may includeinstructions for enabling the electronic device to execute the methodsaccording to the exemplary embodiments stated in the claims and/orspecification of the present invention.

These programs (software modules, software) may be stored in a randomaccess memory, a non-volatile memory including a flash memory, a ROM(Read Only Memory), an EEPROM (Electrically Erasable Programmable ReadOnly Memory), a magnetic disc storage device, a CD-ROM (CompactDisc-ROM), DVDs (Digital Versatile Discs) or an optical storage deviceof other form, and a magnetic cassette. Or, they may be stored in amemory constructed by a combination of some or all of them. Also, eachconstructed memory may be included in plural as well.

Also, the programs may be stored in an attachable storage deviceaccessible through a communication network such as the Internet, anintranet, a LAN (Local Area Network), a WLAN (Wide LAN), or a SAN(Storage Area Network) or a communication network constructed by acombination of them. This storage device may connect to a deviceperforming an exemplary embodiment of the present invention through anexternal port. Also, a separate storage device on the communicationnetwork may connect to a device performing an exemplary embodiment ofthe present invention.

In the aforementioned concrete exemplary embodiments of the presentinvention, a constituent element included in the invention has beenexpressed in the singular number or the plural number in accordance withthe proposed concrete exemplary embodiments. But, the expression of thesingular number or plural number is selected suitable to a situationproposed for description's convenience, and the present invention is notlimited to singular or plural constituent elements. Even the constituentelement expressed in the plural number may be constructed in thesingular number, or even the constituent element expressed in thesingular number may be constructed in the plural number.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: transmitting, to a firstcell, capability information of the terminal including information on aswitching delay time required for an uplink switching between the firstcell and a second cell, wherein an uplink communication for the firstcell and the second cell are configured in a dual connectivity, and aresource of the first cell and a resource of the second cell areallocated on time axis; receiving, from at least one of the first cellor the second cell, an uplink resource allocation information based onthe information on the switching delay time; and performing the uplinkcommunication with the at least one of the first cell or the second cellbased on the uplink resource allocation information.
 2. The method ofclaim 1, further comprising: if a conflict between a first resourceallocated by the first cell and a second resource allocated by thesecond cell occurs, reporting an occurrence of the conflict to the firstcell, wherein the uplink resource allocation information comprisesmonitoring information indicating whether the uplink switching is neededfor a resource allocation.
 3. The method of claim 1, wherein theperforming the uplink communication comprises: transmitting, to thefirst cell, a first uplink signal including a cyclic prefix (CP);performing the uplink switching from the first cell to the second cell;transmitting, to the second cell, a second uplink signal including theCP; and if a timing advance (TA) for the first cell or a TA for thesecond cell is changed, transmitting the changed TA to the first cell.4. The method of claim 1, wherein the performing the uplinkcommunication comprises performing the uplink communication with the atleast one of the first cell or the second cell by using a signalincluding a CP of which a length is determined based on the capabilityinformation of the terminal, and wherein the length of the CP is longerthan a length of an uplink switching time.
 5. The method of claim 1,wherein the first cell is provided by a first base station (BS) and thesecond cell is provided by a second BS.
 6. The method of claim 1,wherein the first cell supports a first radio access technology (RAT),and wherein the second cell supports a second RAT that is different fromthe first RAT.
 7. A method performed by a first cell in a wirelesscommunication system, the method comprising: receiving capabilityinformation of a terminal including information on a switching delaytime required for an uplink switching between the first cell and asecond cell, wherein an uplink communication for the first cell and thesecond cell are configured in a dual connectivity, and a resource of thefirst cell and a resource of the second cell are allocated on time axis;transmitting, to the terminal, an uplink resource allocation informationbased on the information on the switching delay time; and performing theuplink communication with the terminal based on the uplink resourceallocation information.
 8. The method of claim 7, further comprising:receiving a timing advance (TA) for the second cell from at least one ofthe terminal or the second cell; determining an uplink switching time ofthe terminal based on at least one of the switching delay time or the TAof the terminal; and determining a resource to make empty such that alength of the empty resource is equal to or greater than the uplinkswitching time between the first cell and the second cell.
 9. The methodof claim 7, further comprising: transmitting, to the terminal,information indicating a type of scheduling for the terminal, whereinthe type of scheduling indicates whether a resource of the second cellis allocated by the first cell.
 10. The method of claim 7, furthercomprising: transmitting, to the second cell, information necessary forallocating a resource to the terminal; and receiving, from the secondcell, information regarding the resource allocated to the terminal. 11.The method of claim 7, wherein the performing the uplink communicationcomprises performing the uplink communication with the terminal by usinga signal including a CP of which a length is determined based on thecapability information of the terminal, and wherein the length of the CPis longer than a length of an uplink switching time.
 12. The method ofclaim 7, wherein the first cell is provided by a first base station (BS)and the second cell is provided by a second BS.
 13. The method of claim7, wherein the first cell supports a first radio access technology(RAT), and wherein the second cell supports a second RAT that isdifferent from the first RAT.
 14. A terminal in a wireless communicationsystem, the terminal comprising: a transceiver; and at least oneprocessor coupled to the transceiver and configured to: transmit, to afirst cell, capability information of the terminal including informationon a switching delay time required for an uplink switching between thefirst cell and a second cell, wherein an uplink communication for thefirst cell and the second cell are configured in a dual connectivity,and a resource of the first cell and a resource of the second cell areallocated on time axis, receive, from at least one of the first cell orthe second cell, an uplink resource allocation information based on theinformation on the switching delay time, and perform the uplinkcommunication with the at least one of the first cell or the second cellbased on the uplink resource allocation information.
 15. The terminal ofclaim 14, wherein the at least one processor is further configured to:if a conflict between a first resource allocated by the first cell and asecond resource allocated by the second cell occurs, report anoccurrence of the conflict to the first cell, wherein the uplinkresource allocation information comprises monitoring informationindicating whether the uplink switching is needed for a resourceallocation of the terminal.
 16. The terminal of claim 14, wherein the atleast one processor is further configured to: transmit, to the firstcell, a first uplink signal including a cyclic prefix (CP), perform theuplink switching from the first cell to the second cell, transmit, tothe second cell, a second uplink signal including the CP, and if atiming advance (TA) for the first cell or a TA for the second cell ischanged, transmit the changed TA to the first cell.
 17. The terminal ofclaim 14, wherein the at least one processor is further configured to,perform the uplink communication with the at least one of the first cellor the second cell by using a signal including a CP of which a length isdetermined based on the capability information of the terminal, andwherein the length of the CP is longer than a length of an uplinkswitching time.
 18. The terminal of claim 14, wherein the first cell isprovided by a first base station (BS) and the second cell is provided bya second BS.
 19. The terminal of claim 14, wherein the first cellsupports a first radio access technology (RAT), and wherein the secondcell supports a second RAT that is different from the first RAT.